This invention relates to a liquid crystal orientation controlling film made from a specific resin and a liquid crystal display device using such a film.
Liquid crystal display devices of the SBE system, which make use of the super-twisted birefrigence effect (T. J. Scheffer and J. Nehring: Appln. Phys. Leff. 45 (10), 1021 (1984)) are very excellent in contrast and viewing properties in comparison with conventional TN-system liquid crystal display devices.
As the orientation controlling film for such liquid crystal display devices, an inorganic oblique evaporation film made from silicon oxide or other like material has been mainly used for fulfilling the requirement to increase the pretilt angle.
Such inorganic oblique evaporation film, however, has variable selectivity over liquid crystals and is incapable of effecting good orientation of all types of liquid crystal compositions. It also had a problem that the orientation would become nonuniform under high-temperature heating in the assembling process, resulting in a low yield and poor productivity. Further, such film was unable to satisfy the contrast and viewing properties required for the orientation controlling film.
Use of polyimide-isoindoloquinazolinediones as orientation controlling film for liquid crystal display devices is disclosed, for instance, in U.S. Pat. No. 4,278,326. The liquid crystal display device using such a material as the orientation controlling film is low in the tilt angle and thus is not suitable for SBE type liquid crystal display devices.